An axial flow rotary machine, such as a gas turbine engine for an aircraft, communicates hot working fluids through various sections of the machine, and includes a rotor assembly in addition to a plurality of bearing compartments. Each bearing compartment has at least one bearing for supporting the rotating shaft of the rotor assembly. The bearing in the bearing compartment is supplied with a lubricating fluid such as oil, for lubricating its surfaces. A seal assembly extends between the rotating shaft and the bearing compartment to restrict or minimize the leakage of oil from the bearing compartment and the leakage of hot working fluids into the bearing compartment.
A typical seal assembly includes a ring seal, a ring seal outer housing liner, a seal plate and a spacer. Both the seal plate and the spacer rotate together with the rotating shaft and the housing liner is static, while the ring seal is free. The ring seal locates in-between the seal plate and the spacer. The ring seal forms sealing surfaces against the seal plate and the ring seal housing liner, the latter of which encloses the seal assembly.
Current ring seals utilize the outer diameter (OD) of an extension feature on either the spacer or the seal plate to prevent the ring seal element from shifting eccentric to the centerline of the shaft during assembly. This extension feature is radially underneath the ring seal, longitudinally in-between the spacer and the seal plate, and, physically attached to either the spacer or the seal plate.
Advanced, high-performance engines require improved performance from ring seals of the main shaft bearing compartment in addition to meeting more aggressive metrics in cost, weight and reliability for the sealing assembly. In addition, recent engine programs have needed to apply hardface coatings on ring seal contacting surfaces to improve wear resistance.
Such hardface coating requirements might include ring seal contacting surfaces on the ring seal outer housing liner, the rotating spacer and the rotating seal plate. Moreover, recent engine designs have been more aggressive on gapping or physical space/geometry constraints to improve performance. The combination of these challenges has created difficulty when manufacturing the spacer and the seal plate. Specifically, the radial location of the extension feature OD on spacer/seal plate creates a geometry constraint and disadvantageous situation for hardface spray processes. The extension feature OD of the spacer/seal plate is in close proximity to the inner diameter (ID) of the hardface region. As a result, hardface spray processes produced quality defects near the ID of the hardface region. Such defects have impacted and will impact part quality, cost metrics, and part delivery metrics since extra labor and time have to be spent on inspection, removal and repair. It would therefore be beneficial if a solution is found to solve this problem and satisfy the hardface coating and part geometry requirement.